The present invention relates to an outboard engine arrangement.
In general, in an outboard engine arrangement having an engine disposed at an upper level of the arrangement so that its power may be transmitted to a propeller disposed at a lower level to drive the propeller, a transmission is interposed between the engine and the propeller and the rotational speed of the engine is transmitted to the propeller at a predetermined ratio.
With an outboard engine arrangement provided with such transmission, this transmission and an arrangement for lubricating the transmission are obstacles in providing a compactness for the arrangement. For example, in order to permit different types of navigation for a ship, the tranmission in the outboard engine arrangement must be necessarily constructed of a large size. Also, a space is required to store oil for lubricating the transmission.
In the outboard engine arrangement described in Japanese Utility Model Application Laid-open No. 154592/78, a crank shaft of the engine is directly connected with a drive shaft, so that a given step down ratio between the crank shaft and the propeller is provided by the transmission interposed between the drive shaft and the propeller. In such conventional outboard engine arrangement, if the step down ratio is set at a smaller value to modify the outboard engine arrangement into a higher speed type, it is difficult to navigate the ship at an extremely low speed, whilst if the step down ratio is set at a larger value to modify the outboard engine arrangment into a lower speed type the efficiency of navigation of the ship at a higher speed is reduced. Therefore, it is difficult to control the navigation speed with a single outboard engine arrangement over a wide speed range from an extremely low speed to a high speed.
In general, the lubrication of the transmission is carried out by utilizing an oil splash upon operation of the transmission partially immersed in a lubricating oil stored in a tranmission case. In an outboard engine arrangement, however, if primary and sub shafts of the transmission are vertically disposed, gears located at upper positions on the primary and sub shafts are completely exposed above the oil surface and for this reason, it is difficult to lubricate these gears with oil splash. In addition, if such gears are also immersed in the oil, substantially all of the transmission is immersed in the oil and hence, resistance to rotation of the transmission is considerably increased, which is not desirable.